The research, conducted by the University of Sydney and published in the British Medical Journal Open, shows that eating just three to four servings of vegetables—or about three to four fistfuls worth—can reduce stress levels by up to 12 percent. Add in another two or so servings of fruit, the researchers say, and you can decrease stress by up to 14 percent.

The results are even more exciting for women: researchers say women who eat three to four servings of veggies each day can lower their stress levels by 18 percent compared to those who eat one serving a day. Eating fruit has a similar effect. By adding two servings of fruit a day, women can lower stress levels by up to 16 percent. And women who ate five to seven servings of veggies and fruit lowered stress levels by a surprising 23 percent.

"We found that fruit and vegetables were more protective for women than men, suggesting that women may benefit more from fruit and vegetables," said study author Binh Nguyen.

To measure stress levels in 60,000 participants, researchers used a questionnaire that calculates anxiety, gauging participants answers over two points in time. Interestingly, eating fruit alone had no effect on stress levels, the researchers found, while noshing on more than seven servings of vegetables a day did not further decrease anxiety, they say.